Re: [swift-users] Multiple Class Types in Protocol Composition

2017-12-08 Thread Mario Meili via swift-users 
Hi Slava,

Thank you very much for the quick response. As you requested, I filed the bug 
under the following link: https://bugs.swift.org/browse/SR-6561

Best Regards
Mario

From: <spes...@apple.com> on behalf of Slava Pestov <spes...@apple.com>
Date: Thursday, 7 December 2017 at 22:27
To: Mario Meili <mario.me...@live.com>
Cc: "swift-users@swift.org" <swift-users@swift.org>
Subject: Re: [swift-users] Multiple Class Types in Protocol Composition

Hi Mario,

You’re right that this part of the proposal was not fully implemented. 
Computing the common ancestor of two superclasses is a little tricky here 
because it would force us to resolve the superclass type of a class when 
realizing a subclass existential. This would introduce circular dependencies. 
Either I missed something obvious or it would require some re-architecting of 
the type checker to make it work.

Either way, yes it’s a known limitation, but not one that is tracked by a JIRA 
presently, so please do file a bug!

Thanks,

Slava


On Dec 7, 2017, at 7:17 AM, Mario Meili via swift-users 
<swift-users@swift.org<mailto:swift-users@swift.org>> wrote:

Hi everyone,

I noticed strange behaviour of the Swift 4.0.3 compiler regarding class and 
subtype existentials.

According to the proposal SE-0156 
(https://github.com/apple/swift-evolution/blob/master/proposals/0156-subclass-existentials.md<https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fapple%2Fswift-evolution%2Fblob%2Fmaster%2Fproposals%2F0156-subclass-existentials.md=02%7C01%7C%7Cf12145f448334d2a644c08d53db941d1%7C84df9e7fe9f640afb435%7C1%7C0%7C636482788230444913=bjKRAVds%2BubJz5Mpi27bQmpbBigAfekf%2FiXopHekabE%3D=0>),
 multiple class types in protocol compositions should be allowed, if:


  *   The class types are the same
  *   Or, one class type must be a subtype of the other.

However, when copying the exact code from the proposal into Xcode 9.2, the 
result is the following:



My conclusion here is that the compiler does not allow multiple class types in 
one protocol composition.

My question is:
Is this behaviour intended or should I open a bug report?

Thank you very much

BR
Mario
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Re: [swift-users] Multiple Class Types in Protocol Composition

2017-12-07 Thread Slava Pestov via swift-users 
Hi Mario,

You’re right that this part of the proposal was not fully implemented. 
Computing the common ancestor of two superclasses is a little tricky here 
because it would force us to resolve the superclass type of a class when 
realizing a subclass existential. This would introduce circular dependencies. 
Either I missed something obvious or it would require some re-architecting of 
the type checker to make it work.

Either way, yes it’s a known limitation, but not one that is tracked by a JIRA 
presently, so please do file a bug!

Thanks,

Slava

> On Dec 7, 2017, at 7:17 AM, Mario Meili via swift-users 
>  wrote:
> 
> Hi everyone,
>  
> I noticed strange behaviour of the Swift 4.0.3 compiler regarding class and 
> subtype existentials.
>  
> According to the proposal SE-0156 
> (https://github.com/apple/swift-evolution/blob/master/proposals/0156-subclass-existentials.md
>  
> ),
>  multiple class types in protocol compositions should be allowed, if:
>  
> The class types are the same
> Or, one class type must be a subtype of the other.
>  
> However, when copying the exact code from the proposal into Xcode 9.2, the 
> result is the following:
>  
> 
>  
> My conclusion here is that the compiler does not allow multiple class types 
> in one protocol composition.
>  
> My question is:
> Is this behaviour intended or should I open a bug report?
>  
> Thank you very much
>  
> BR
> Mario
> ___
> swift-users mailing list
> swift-users@swift.org 
> https://lists.swift.org/mailman/listinfo/swift-users 
> 

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[swift-users] Multiple Class Types in Protocol Composition

2017-12-07 Thread Mario Meili via swift-users 
Hi everyone,

I noticed strange behaviour of the Swift 4.0.3 compiler regarding class and 
subtype existentials.

According to the proposal SE-0156 
(https://github.com/apple/swift-evolution/blob/master/proposals/0156-subclass-existentials.md),
 multiple class types in protocol compositions should be allowed, if:


  *   The class types are the same
  *   Or, one class type must be a subtype of the other.

However, when copying the exact code from the proposal into Xcode 9.2, the 
result is the following:

[cid:image001.png@01D36F76.E9815E30]

My conclusion here is that the compiler does not allow multiple class types in 
one protocol composition.

My question is:
Is this behaviour intended or should I open a bug report?

Thank you very much

BR
Mario
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